Principal Safety Methods Engineer

TerraPower is a nuclear technology company based in Bellevue, Washington. At its core, the company is working to raise living standards globally through a more affordable, secure, and environmentally friendly form of nuclear energy along with innovations in medical isotopes to improve human health. In 2006, TerraPower originated with Bill Gates and a group of like-minded visionaries who evaluated the fundamental challenges to raising living standards around the world. They recognized energy access was crucial to the health and economic well-being of communities and decided that the private sector needed to take action and create energy sources that would advance global energy deployment. TerraPower’s mission is to be a world leader in new nuclear technologies, while developing innovators and future leaders in the nuclear field. As a result, the company’s activities in the fields of nuclear energy and related sciences are yielding significant innovations in the safety and economics of nuclear power, hybrid energy and medical applications – all for significant human health benefits.” TerraPower is seeking to hire highly motivated and forward-thinking professionals who are interested in focusing on advanced nuclear reactor research and development and influencing change within the nuclear power landscape and bringing forward the critical production of medical isotopes. TerraPower is an Equal Opportunity Employer. We do not discriminate in hiring on the basis of sex, gender identity, sexual orientation, race, color, religious creed, national origin, physical or mental disability, protected Veteran status, or any other characteristic protected by federal, state, or local law. Principal Safety Methods Engineer This role supports the development, enhancement, and deployment of plant‑scale thermal‑hydraulic analysis methods and models for the Natrium reactor. Reporting to the Manager, Plant Thermal Hydraulics Methods, the principal engineer supports the creation, improvement and qualification of advanced system-level modeling approaches that enable accurate, robust prediction of plant behavior across operational and transient scenarios. The position requires expertise in system‑level thermal‑hydraulics, thermal‑fluids behavior, computational methods, and scaling analysis supporting benchmarking computational models against experimental data. Responsibilities Support verification, validation, and uncertainty quantification activities for plant scale thermal-hydraulic analysis tools. Develop and execute code assessment plans, including validation matrices, test selection, and quantitative comparison methodologies. Perform scaling analysis to evaluate the applicability of test data to reference system conditions, including assessment of similarity criteria and scaling distortion. Interpret and apply experimental data from separate effects and integral test facilities to support model validation and closure of technical gaps. Define validation needs, develop test requirements, and collaborate closely with test engineering teams to ensure alignment between model gaps and experimental programs. Document V&V methodologies, model assumptions, validation results, and uncertainty analyses for internal design processes and regulatory submittals. Collaborate with multidisciplinary teams to support plant design, safety analysis, and licensing workflows. Apply and improve TerraPower’s SQA and NQA1 modeling quality practices and ensure traceability and configuration control of analysis inputs, models, and results. Mentor junior engineers in system modeling, validation methodologies, and best practices in code assessment. Key Qualifications and Skills Degree in Mechanical, Nuclear, Chemical Engineering, or similar field, with 8 plus years in the field of system‑level thermal‑hydraulic analysis and code assessment for nuclear or complex energy systems. Demonstrated experience in code assessment, including model-to-test comparison, validation metric development, and uncertainty quantification. Hands‑on experience working with experimental thermal‑hydraulic data, including data analysis, uncertainty evaluation, and comparison against system‑level predictions. Proficiency with system analysis tools (e.g., RELAP5‑3D, TRACE, SAS, or equivalent) applied to plant‑scale transient and steady-state evaluations. Strong foundation in thermal-fluid and reactor system behavior considerations relevant to advanced reactor designs. Experience performing scaling analysis to ensure appropriate translation test-scale phenomena, including application of similarity criteria and detailed scaling distortion impact qualifications. Experience developing validation strategies, defining data needs, and coordinating with experimental programs. Experience with SQA and NQA‑1 quality assurance practices for modeling workflows is highly preferred. Strong analytical thinking, clear technical communication, and the ability to manage multiple validation tasks in parallel. This position is subject to qualification requirements in accordance with ANSI/ANS 3.1. Candidates must meet the minimum education and experience criteria applicable to the role, including relevant nuclear industry experience where required. Verification of data will be part of the hiring process. Job Functions: Job Functions are physical actions and/or working conditions associated with the position. These functions may also constitute essential functions for the job which the employee must be able to fulfill, with or without accommodation. Information provided below is to help describe the job so that the applicant has a reasonable understanding of the job duties/expectations. An applicant's ability to perform and/or tolerate these actions and conditions will be discussed and workplace accommodations may be made on a case-by-case basis following an individualized assessment of the applicant and other considerations, including but not limited to any governing safety standards. Motor Abilities: Sitting for extended periods, bending/stooping, grasping/gripping, fine motor control (hands) Physical exertion and/or requirements: Minimal, with ability to safely lift up to 25 pounds. Repetitive work: Prolonged Special Senses: Visual and audio focused work Work Conditions: Stairs, typing/keyboard, standard and/or sitting working environment of >8 hours/day Travel required 0-10% TerraPower’s technology is controlled for export by various agencies of the U.S. Government. TerraPower must evaluate applicants who are foreign nationals (other than asylees, refugees, or lawful permanent residents) in accordance with U.S. Government export control requirements. To facilitate TerraPower’s export control reviews, you will be asked as part of the application process to identify whether you are a U.S. Citizen or national, asylee, refugee, or lawful permanent resident of the United States. Government export authorization approval times vary. Based on the business needs for a particular position, TerraPower may not consider a foreign national from a country if it is impracticable to obtain timely Government export approval. Job details Salary Range: $168,316 - $252,475 Any salary offered within the posted salary band is based on market data and commensurate with the selected candidate’s qualifications and experience. This range is specific to Washington State. Job Type: Full-time Benefits: Competitive Compensation Salary, eligible to participate in discretionary short-term incentive payments Comprehensive Medical and Wellness Benefits Medical Vision Dental Life and Disability Gender Affirmation Benefits Parental Leave 401k Plan Generous Paid Time Off (PTO) 21 days of annually accrued PTO Generous Holiday Schedule 10 paid holidays Relocation Assistance Professional and Educational Support Opportunities TerraPower Career and Benefits information: